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In cataract and refractive surgery, the eyelids are a source of gram-positive and other types of bacteria that carry the threat of postoperative infection. Two common methods used to reduce the risk of infection from eyelid bacteria are preoperative prophylaxis with antibiotics and performing lid scrubs. The latter involves various techniques of scrubbing the lid margin to remove bacteria and the debris that traps them. My colleagues and I conducted a study to evaluate the efficacy of these preoperative methods to reduce the bacterial load of the eyelids and conjunctiva.
STUDY DESIGN
We randomized 74 precataract patients into four groups. Group 1 was the control and received no antibiotic prophylaxis or lid scrubbing prior to undergoing surgery. The second group received antibiotic prophylaxis only. We instructed these patients to use the antibiotic q.i.d. for 2 days prior to surgery as well as one application on the morning of the procedure. Group 3 performed lid scrubbing only—q.h.s. for 2 nights preoperatively. Group 4 received both antibiotic prophylaxis and lid scrubbing. They performed lid scrubbing q.h.s. for 2 preoperative nights and used levofloxacin q.i.d. for 2 preoperative days and once on the morning of surgery.
We then took preoperative cultures of each patient's lids and conjunctiva (together as one culture) on the morning of surgery, and we analyzed the number of colony-forming bacterial units that developed in the microbiological laboratory (Table 1).
RESULTS
The control group showed an average of 1,695 colony-forming units. The cultures of Group 2, who underwent prophylaxis with levofloxacin only, revealed a unit count of 1,078, which was 36% less than that of the control group. That result barely reached statistical significance (P=.049), which we had anticipated. Unexpectedly, however, Group 3, who underwent lid scrubbing alone yielded the highest number (2,493) of colony-forming units, a count 47% greater than that of the control group. We hypothesized that lid scrubbing releases the oils from the meibomian glands as well as the scruff and scaly skin on the lid margin that trap staphylococci bacteria and other species. Thus, lid scrubbing may expose the ocular surface to more bacteria.
Interestingly, when we combined lid scrubbing with antibiotic application, patients experienced a dramatic decrease of approximately 84% (279) in colony-forming units compared with the control group. Lid scrubbing seems to make the bacteria more available to the antibiotic for killing. In summary, therefore, lid scrubbing alone was rather ineffective, antibiotic therapy alone was somewhat effective, but lid scrubbing combined with antibiotic use was the most efficacious preoperative treatment for reducing the bacterial load (Table 2).
DISCUSSION
Many ophthalmologists now recommend lid scrubbing prior to refractive surgery to avoid diffuse lamellar keratitis (some of the toxins and bacteria on the eyelids are thought to cause this condition). Performing lid scrubbing without a prophylactic antibiotic, however, may actually increase the patient's chances for postoperative infection or inflammation. I believe that physicians who plan to perform preoperative lid scrubbing should concomitantly use a broad-spectrum fluoroquinolone antibiotic. An antibiotic used alone may not reach all of the bacteria, and lid scrubbing dislodges bacteria from underneath the lid margins and exposes it to the antibiotic.
